Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$162.50	11.222%	$180.7358	$180.74	$180.75	$180.70
Purchase #2	$41.64	6.247%	$44.2413	$44.24	$44.25	$44.20
Purchase #3	$13.66	9.697%	$14.9846	$14.98	$15.00	$15.00
Purchase #4	$250.80	12.379%	$281.8465	$281.85	$281.85	$281.80
Purchase #5	$107.33	3.803%	$111.4118	$111.41	$111.40	$111.40
Purchase #6	$172.89	10.485%	$191.0175	$191.02	$191.00	$191.00
Purchase #7	$184.52	13.592%	$209.6	$209.60	$209.60	$209.60
7 purchase totals =	$933.34		$1,033.8375	$1,033.84	$1,033.85	$1,033.70